Java I/O

Update: The second edition of the Java I/O has been published. I'm keeping this page here to support readers who bought the first edition, as well as for readers of translations, since many of the translations are still based on the first edition. However, if you want the most current information, you should go to the second edition page instead.

The second edition is substantially improved over the second edition with lots of new and updated material. New topics include Java 1.4, 5, and 6, including the New I/O APIs, Bluetooth, USB, and J2ME. It is completely up-to-date with the state of the art in Java as of Java 6. If you're buying a new copy, you'll want to make sure you get the second edition. It's the one with the rabbit on the cover.

What a long strange trip this book has been. When I began writing the first draft back in September, 1997, I thought it would take me about two months and 200 pages. Now, a year and a half and 600 pages later, I've learned that I/O is a much bigger, more interesting, and more important topic than I originally dreamed. But I have managed to create what is unquestionably the best book I've ever written, and one in which I expect that all Java programmers will find something worthwhile, so I hope you won't mind if I take a few minutes to tell you about this book.

Java's input and output libraries have been unfairly maligned for some time. It is widely (but incorrectly) believed that I/O in Java is a lot weaker and a lot harder than I/O in traditional languages like C, C++, and Pascal. If anything, however, the exact opposite is true. Java's I/O tools are far more sophisticated, more powerful, and easier to use than traditional printf()/scanf() style I/O.

Java I/O tells you all you need to know about the four main categories of streams and uncovers less known features to help make your I/O operations more efficient. Plus, it shows you how to control number formatting, use characters aside from the standard ASCII character set, and get a head start on writing truly multilingual software.

I/O in C, C++, and most other languages, is hamstrung by the assumption that what's being read or written is a 1970s era dumb terminal, or at least something very much like it. Java is the first major language to throw out this assumption. The designers of Java recognized that programs that read and write files, network connections, and serial port devices are a lot more important than toy programs from CS101 that read a number from the command line and square it. Consequently they created a language that focuses on solving professional programmers' real problems, instead of CS101 textbook examples. Rather than copying old-fashioned I/O APIs based on dumb ASCII terminals from the 1970s or DOS prompts from the 1980s, Java's designers created a new I/O API based on abstract streams. This API better suits the international network programs of the 1990s.

Unfortunately, precisely because Java I/O is structured so differently from I/O in the languages most of us grew up with, many programmers don't realize how simple and powerful it really is. I first noticed this after I wrote Java Network Programming. Many of the questions I got from readers weren't about network programming at all. They were about I/O. That's when I began thinking seriously about writing a prequel to Java Network Programming; a book that would cover the java.io package and show programmers how to really take advantage of Java's I/O facilities to write very powerful programs far more quickly than they could in any other language. Java I/O is that book.

Here are just a few of the topics covered in depth in Java I/O:

• How to take advantage of the polymorphic nature of InputStream and OutputStream
• Files and network connections, the two most common sources of input and output
• Filter streams
• Reading and writing text
• Padding and aligning numbers
• Communicating with serial and parallel port devices
• The Java Cryptography Extension
• Object Serialization
• Data Compression
• Writing file access code that works across platforms
• File dialogs in both the classic AWT and Swing

And that's really just the beginning of what you'll learn from Java I/O. I'm really happy with this book. In fact it's perhaps the first book I've written that I really feel reached its full potential. I do hope you'll check it out. It's available from amazon.com, Fat Brain, and other purveyors of fine computer books. If you need to special order it, the ISBN number is 1-56592-485-1. It's $32.95, 596 pages, published by O'Reilly, and written by me, Elliotte Rusty Harold.

Table of Contents

Preface

Part I: Basic I/O

1. Introducing I/O

• What Is a Stream?
• Numeric Data
• Character Data
• Readers and Writers
• The Ubiquitous IOException
• The Console: System.out, System.in, and System.err
• Security Checks on I/O

2. Output Streams

• The OutputStream Class
• Writing Bytes to Output Streams
• Writing Arrays of Bytes
• Flushing and Closing Output Streams
• Subclassing OutputStream
• A Graphical User Interface for Output Streams

3. Input Streams

• The InputStream Class
• The read( ) Method
• Reading Chunks of Data from a Stream
• Counting the Available Bytes
• Skipping Bytes
• Closing Input Streams
• Marking and Resetting
• Subclassing InputStream
• An Efficient Stream Copier

Part II: Data Sources

4. File Streams

• Reading Files
• Writing Files
• File Viewer, Part 1

5. Network Streams

• URLs
• URL Connections
• Sockets
• Server Sockets
• URLViewer

Part III: Filter Streams

6. Filter Streams

• The Filter Stream Classes
• The Filter Stream Subclasses
• Buffered Streams
• PushbackInputStream
• Print Streams
• Multitarget Output Streams
• File Viewer, Part 2

7. Data Streams

• The Data Stream Classes
• Reading and Writing Integers
• Reading and Writing Floating-Point Numbers
• Reading and Writing Booleans
• Reading Byte Arrays
• Reading and Writing Text
• Miscellaneous Methods
• Reading and Writing Little-Endian Numbers
• Thread Safety
• File Viewer, Part 3

8. Streams in Memory

• Sequence Input Streams
• Byte Array Streams
• Communicating Between Threads with Piped Streams

9. Compressing Streams

• Inflaters and Deflaters
• Compressing and Decompressing Streams
• Working with Zip Files
• Checksums
• JAR Files
• File Viewer, Part 4

10. Cryptographic Streams

• Hash Function Basics
• The MessageDigest Class
• Digest Streams
• Encryption Basics
• The Cipher Class
• Cipher Streams
• File Viewer, Part 5

IV. Advanced and Miscellaneous Topics

11. Object Serialization

• Reading and Writing Objects
• Object Streams
• How Object Serialization Works
• Performance
• The Serializable Interface
• The ObjectInput and ObjectOutput Interfaces
• Versioning
• Customizing the Serialization Format
• Resolving Classes
• Resolving Objects
• Validation
• Sealed Objects

12. Working with Files

• Understanding Files
• Directories and Paths
• The File Class
• Filename Filters
• File Filters
• File Descriptors
• Random-Access Files
• General Techniques for Cross-Platform File Access Code

13. File Dialogs and Choosers

• File Dialogs
• JFileChooser
• File Viewer, Part 6

14. Multilingual Character Sets and Unicode

• Unicode
• Displaying Unicode Text
• Unicode Escapes
• UTF-8
• The char Data Type
• Other Encodings
• Converting Between Byte Arrays and Strings

15. Readers and Writers

• The java.io.Writer Class
• The OutputStreamWriter Class
• The java.io.Reader Class
• The InputStreamReader Class
• Character Array Readers and Writers
• String Readers and Writers
• Reading and Writing Files
• Buffered Readers and Writers
• Print Writers
• Piped Readers and Writers
• Filtered Readers and Writers
• File Viewer Finis

16. Formatted I/O with java.text

• The Old Way
• Choosing a Locale
• Number Formats
• Specifying Width with FieldPosition
• Parsing Input
• Decimal Formats
• An Exponential Number Format

17. The Java Communications API

• The Architecture of the Java Communications API
• Identifying Ports
• Communicating with a Device on a Port
• Serial Ports
• Parallel Ports

Part V: Appendixes

A. Additional Resources

B. Character Sets